After the wild and unexpected runaway success of Taken, Liam Neeson has found himself as a surprise action-star, and continues in that same vein here. He plays Dr. Martin Harris, a lecturer on his way to a biotechnology summit in Berlin, along with his wife, Mad Men's January Jones. After a tragic and crunching car accident leaves him in a coma for four days, Harris awakes to find that his wife doesn't recognise him, and that there is another man claiming his name, his job and his entire life - past, present and future. Is Harris simply suffering delusions and amnesia as a result of his coma? Or is something more sinister afoot?

It's initially intriguing. Did Harris imagine being married to January Jones in the earlier scenes? Why would she lie? As a bemused Harris asks, "Do you know what it feels like to go insane, Doctor? Do you believe what people tell you, or what you know?" That's an interesting idea for the film to explore, but unfortunately the film never really allows Harris, or the audience, to believe that trauma-induced-insanity is really an option. This is an action film, and we know it. When the man a paranoid Harris (correctly) believes is following him turns up at the hospital, things are confirmed as being much more sinister than just a bit of a concussion.

Having nowhere else to turn, Harris tracks down Diane Kruger's Gina - an illegal immigrant, and the driver behind the wheel of his crashed taxi, and tries, as so many wronged action stars do, to get his life back. While Neeson is largely going through the motions, Diane Kruger, despite an awful Bosnian accent, gives off a warmth that the film lacks when she isn't on-screen, and adds some much needed life to proceedings, especially when compared to January Jones' wooden performance as Mrs. Harris (Or is that just a part of her character? Another mystery.)

Also outshining Neeson is Bruno Ganz as an ex-Stasi private investigator whom he and Gina turn to for help. His Jürgen is a character that could have come from any number of spy thrillers, but Ganz plays him with such verve and class that he easily stands out here. Perhaps the real star of the show, however, is the city of Berlin, which is the beneficiary of some stunning cinematography from Spanish born Flavio Labiano.

As has become the standard for action films in this post-Bourne world, the whole thing is shot by director Jaume Collet-Serra (Orphan, House of Wax) in a gritty, frenetic style; all green-tints and quick edits. In fact, it's rare for any shot in the film to last more than a few seconds, but unfortunately the action never feels as real or as natural as it does in Doug Liman and Paul Greengrass’ superior franchise. Too perfunctory and controlled, you can almost hear the stunt-men high-fiving each other.

Ultimately, Unknown is content to drag Neeson through the action-hero motions, and produces an expected, yet entirely unsatisfying twist. While it's good that the film doesn't play the ambiguity in the story for too long (take a bow, Flightplan), the developments and reveals are so implausible that they invalidate most of what came before, and compromise the audience's sympathies for the characters.

The action picks up towards the end and there are some fiery explosions, but by that point will anyone still care? If you're willing to just go with the flow, Unknown is a perfectly enjoyable, Bourne-lite action thriller, with a few good performances and some beautiful use of its Berlin setting, but the longer it goes on the more it stretches credibility, and the more you think about it, the less the whole thing holds together.